This invention relates to devices for land vehicle engines and more specifically to roller valve lifter assemblies or roller cam followers for high load engines that may include high speed automotive racing engines. The new roller cam follower incorporates a sleeved bushing plane cam follower bearing with an oil pressure lubricating system.
In the field of high performance engines, roller cam followers or valve lifters typically have needle or pin roller cam follower bearings. These bearings may be designed for side lubrication or other lubrication methods and may be prone to short life or premature failure when subjected to relatively high valve spring loads and rpm levels because the needle rollers may be the weakest link. The easily compromised needle rollers may be subject to rapid erosion and the resulting increase in radial bearing clearance may cause catastrophic failure of a cam follower bearing, valve lifter or other critical engine components.
A known use of a plane bearing or bushing in place of the traditional needle or pin roller bearing is disclosed in U.S. Pat. Nos. 5,127,374 and 5,178,107 for use in an internal combustion engine block used in high speed motor vehicles having open-ended cylindrical bores in which valve lifters reciprocate. A roller may have a bushing press fit therein for the bushing to rotate on an axle or pin of a roller valve lifter. However, because such a bearing may require a generous supply of constant lubrication to the interior surface, a lubrication oil passage is formed within the pin or axle that may be a V-shape. The lubrication oil passage may compromise the integrity of the pin by weakening it substantially and may create a significant stress riser formed at the intersection of two holes drilled to form a V-shaped passage. The teaching is to deliver oil to the center of the bearing and axle interface. This may cause low reliability in a high speed automotive motor vehicle engine due to the harsh environment of heavy valve spring loads and impact forces due to valve float. These two patents were issued approximately twenty years ago and to applicant's knowledge as one involved in vehicle motor engine designs, this disclosed invention has not found use in high speed motor vehicle engines.